3 Observations From the Largest Tornado Outbreak in History

Tornado paths on April 3-4, 1974.  Image credit: T. Fujita.

Tornado paths on April 3-4, 1974. Image credit: T. Fujita.

Growing up, I was obsessed with tornadoes.  I daydreamed about them.  I watched every TV show about them.  I read every book I could find about them – several times.  And, in those books, there was only one tornado outbreak that was always  mentioned: the Super Outbreak (April 3-4, 1974).  It was the grand-daddy of all outbreaks – a veritable monolith of atmospheric violence.  Even to this day, its statistics still stun: 2 days, 148 tornadoes, 13 states, 30 violent tornadoes, 6 F5 tornadoes, and 315 dead.  It was the benchmark; no other outbreak was even close.  Sure, the Palm Sunday Outbreak of 1965 was a doozy, but it was at least a couple notches below the Super Outbreak.  It was an outbreak so monstrous that most thought its rival would not come for many lifetimes.

Visible satellite presentation of the 2011 Super Outbreak.

Visible satellite presentation of the 2011 Super Outbreak.

Then, from April 26 to April 28 of 2011, the unthinkable happened: another – even bigger – super outbreak of tornadoes ravaged the Southeast.  This time, at least 350 tornadoes occurred across 14 states – including several long-lived, violent tornadoes – killing over 300 people.   With its massive number of tornadoes, it easily became the largest tornado outbreak in American history.  Of these tornadoes, 15 achieved violent ratings (EF4/EF5), and – perhaps – several more would have had this outbreak occurred in the era of lower ratings standards.

Violent tornado near Philadelphia, MS on April 27, 2011.  Photo credit: Dick McGowan

Violent tornado near Philadelphia, MS on April 27, 2011. Photo credit: Dick McGowan

Beyond sheer numbers, though, there are many noteworthy aspects of this outbreak.   One was the large number of highly-visible tornadoes (see right).  As most storm chasers know, the Southeast isn’t exactly known for visually-impressive tornadoes: fast storm motion, heavy precipitation, high trees, and (of course) darkness often make viewing difficult. Yet, many of the 2011 Super Outbreak tornadoes were highly visible – even at a distance (see 0:40 in this video for an example). I’ve seen several videos of expansive rain-free bases with large tornadoes – almost as if these storms were on the low-precipitation side of the supercell continuum. The only exception seems to be the tornadoes that occurred near the warm front, where lower cloud bases made visibility characteristically tough.

Another fascinating part of this outbreak was the high number of smaller vortices within these tornadoes. The Cullman tornado, in particular, was a vortex bonanza. Horizontal vortices, subvortices – even vortices within vortices – were a common sight. And, of course, who can forget the Tuscaloosa tornado? It contained nearly-ubiquitous “octopus tentacles” – a sight so scary that even the editors of “Weekly World News” would have been powerless to make it more frightening.  Additionally, it also featured an invisible, rolling horizontal tube on the front side of the tornado – almost as if the tornado was a giant mower, trimming down the environmental vorticity.  Other major-league tornadoes have produced similar vortices, including the Red Rock tornado (4/26/91), the Moore tornado (5/3/99), and the El Reno tornado (5/24/11).   These vortices are quite rare, as it seems only the most intense tornadoes produce them.

Developing convection in eastern Missippi at 1856 UTC on April 27, 2011.

Developing convection in eastern Missippi at 1856 UTC on April 27, 2011.

Finally, these storms displayed an organization in their incipient supercell stage that I’ve never seen. On a given tornado day, most supercells take a good half-hour to an hour to organize themselves into the characteristic pendant shape on radar. These storms, however, wasted no time. Even before they “broke the cap,” these storms appeared to be rotating.  More fascinating still, the developing convection in eastern Mississippi (see right) displayed a periodicity between storms that I’ve never seen. In that north-south line, at least 14 developing storms can be identified on radar, with a wavelength ranging from 5 – 10 miles. Interestingly, the more intense the storm in that line became, the greater the distance between it and other storms (as one might expect from storm-scale pressure perturbations).

Are there any other aspects of the outbreak that you find interesting?   If you experienced the outbreak(s), what was your experience?


About Gabe Garfield

B.S. and M.S in Meteorology from the Univ. of Oklahoma | Storm Chasing | Extreme Weather | Business at the Univ. of Tennessee | Psalm 97:4
This entry was posted in General, Weather and tagged , , , , , , , , , . Bookmark the permalink.

8 Responses to 3 Observations From the Largest Tornado Outbreak in History

  1. allthingsgeography1 says:

    “On a given tornado day, most supercells take a good half-hour to an hour to organize themselves into the characteristic pendant shape on radar. These storms, however, wasted no time. Even before they “broke the cap,” these storms appeared to be rotating.”

    I remember the sitting in the meteorology lab at the University of Nebraska-Lincoln looking at radar on April 27 and noted the same thing…the storms seemed to start spinning like table tops as soon as they began firing up. It was the most ridiculous thing I’d ever seen. The structures themselves, once well-developed were incredibly well-organized and textbook supercells. The debris-balls were obvious just using traditional reflectivity. Beyond that, I think just the sheer number of cities and towns being blasted by tornadoes was shocking. I honestly expected a large death toll…and by large I mean many dozens, what you might expect from a bad outbreak in the 2010s. But the number of people killed in just the Tuscaloosa-Birmingham tornado alone was 60+ (as the tornado went through densely populated Tuscaloosa and Jefferson Counties). The sheer number of deaths…in the hundreds…was beyond mind-numbing. Geographically, this tornado outbreak was just the perfect storm…high concentration of tornadoes hitting densely populated areas (this includes small towns where the population is locally dense compared to the open country). Very sad indeed, hopefully we won’t see an outbreak like that in a very long time.

    • Yeah, the organization of these storms was phenomenal. Another friend pointed out that these storms maintained virtually the same shape from inception to demise. The only thing that changed was the scale (i.e., the storms just got bigger).

      As you mentioned, the scale of the outbreak was unreal. I tried to keep up with every tornadic supercell in the outbreak in real-time, but that was simply impossible. It was just that massive.

      The death toll was shocking indeed. It really highlights some deficiencies in our assumptions about tornado safety (i.e., increasing warning tech would continue to decrease the number of fatalities). The number of mobile homes is growing rapidly (especially in the Southeast), owing to our continuing economic woes. Unfortunately, this is putting a greater number of people at higher risk in tornado prone areas. We’ve got a lot of work to do!

      Thanks for commenting!

  2. allthingsgeography1 says:

    Reblogged this on All Things Geography.

  3. chris says:

    Very interesting, I am so glad to see someone finally write about this. I was live streaming news from Tuscaloosa, on my cell phone with Dennis Sherrod while he chased Tuscaloosa, and was running GR2 Analyst and Threat Net while watching the entirety of April 27th unfold in real-time, The enormity of progression and staggering atmospheric calculus was blowing my mind.

    I can only suggest, that for some reason, certain ‘rules’ may have changed, or traditional calculus may be lacking adequate definition. For another example, the Joplin EF5 morphed from an undercut imbedded storm to a mile wide EF5 tornado in nearly a minute, just staggering. I saw ‘supercell’ rules seemingly being rewritten with scalar dimensional increase and number on May 24th, 2011 in Oklahoma, and a similar manifestation the following year on April 14th, 2012, in Oklahoma/Kansas. Granted these outbreak days were not the enormity (luckily) of April 27th, 2011, but I would love to see an atmospheric physics and calculus guru (Karen) who was in the field during one of these outbreak days, who may be willing to write a calculus case study detailing this aggressive dynamic of fast-birthing tornadoes and tight tornado clusters. Just like ocean wave height and ship building orthodoxy faced a challenge with documentation of the Draupner rogue wave theory, maybe a new math description would add meaning to this, dare I say trend? Just a thought. I love this article.

  4. Clayton says:

    Nice article, Gabe. I really enjoyed it. I just remember driving over from Atlanta to begin my chase, looking at a picture from the first Cullman tornado, and thinking, “This may be historic.” The tornado just didn’t look like anything you would expect in Alabama, more like Oklahoma.

    Upon arriving in Birmingham, I was targeting the Tuscaloosa storm. The tornado missed my brother’s apartment at Alabama two miles to the north and hardly anybody could make a call to check on anyone. I think when that happened and as things evolved, that was my “May 3rd” moment where the thrill of chasing was completely replaced with sickness.

    By the time the storm had made it to the northside of Birmingham, it was pretty well rain-wrapped so I didn’t really get anything photo-worthy. Driving back to Atlanta at night was an adventure as well, trying to stay ahead, dodge supercells. It was just an emotional day with what happened in Tuscaloosa and knowing so many people in Alabama had been killed (and storms were still ongoing closer to my hometown later that evening). Once back in Atlanta, watching that same Tuscaloosa storm that had formed in MS move into NC was surreal.

    I’ve chased many times in OK, TX, KS, but none of those days even touched this one and that’s something I never thought I’d say.

    • CC Fain! Good to hear from you, sir!

      I am glad you enjoyed the article! 🙂

      Yeah, the Cullman tornado wasn’t your typical AL twister – it was, simply, an aesthetic marvel (and ferocious, too).

      I can’t even imagine how ugly that must’ve been for you in that moment (when Tuscaloosa was getting hit). I felt something similar during the Norman tornado last year: I saw the tornado as it was heading right for my parent’s place. It missed them by 300 yards.

      Yeah, dodging supercells is right! There were so, so many that day. You really couldn’t pick a spot in C/N AL that was immune to their threat. Personally, I don’t even think an outbreak like that one is possible in Oklahoma. You just don’t get huge shear with large CAPE and 0 CIN for hours (with a supercell mode). You may not have ended up with great pics, but you can say you chased the largest tornado outbreak in American history. And that’s something!

      • Clayton says:

        This is certainly true and to think how HUGE we thought April 15th in the same area was. I thought that would be the best chase day by far for me that season. Two weeks later, mother nature raised the bar even further. I’ll never forget the experiences from both of those days. Especially driving through Birmingham and driving over insulation (from who knows where).

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